This invention is directed to an improved dimmer control and dimmer override for use with a display device such as a CRT (cathode ray tube).
CRTs are frequently used to display graphics and other types of video under ambient light conditions which can vary greaty. Accordingly, it is helpful if the CRT is controlled by a dimmer so that image brightness is increased as the intensity of ambient light increases. When the intensity of ambient light decreases, the brightness of the image may be correspondingly decreased.
Under certain conditions, however, it is preferred that the CRT image be at maximum brightness, irrespective of ambient light conditions. For example, when the CRT is to display a warning or emergency message, a bright image is desired to ensure that the emergency message is easily readable. This override of the dimming function also helps to highlight the emergency message so it is more easily distinguished from a routine message.
Another criteria for CRT controls which provide the functions described above is that they be simple, reliable, and inexpensive, particularly for high volume consumer applications.
Accordingly, it is a general object of the invention to provide an improved dimmer control and dimmer override for a display device such as a cathode ray tube.
It is a more specific object of the invention to provide a dimmer and dimmer override control which is relatively simple, inexpensive, and reliable.